CAMPERI Silvia Andrea
A Simple Protocol for Combinatorial Cyclic Depsipeptide Libraries Sequencing by Matrix Assisted Laser Desorption/Ionisation Mass Spectrometry
J. M. GUREVICH-MESSINA; S. L. GIUDICESSI; M. C. MARTÍNEZ-CERON; G. ACOSTA; R. ERRA-BALSELLS; O. CASCONE; F. ALBERICIO; S. A. CAMPERI
Journal of Peptide Science
Año: 2015 vol. 21 p. 40 - 40
Short cyclic peptides have a growing interest in therapeutic, diagnostic and affinity chromatography applications due to their higher selectivity and resistance to enzymatic degradation than their linear counterparts. One-bead-one-peptide libraries combined with mass spectrometry allow the screening and identification of suitable ligands for any target protein. Although linear peptides can be readily sequenced by MS, cyclic peptides typically yield complex fragment ion mass spectra. To do easier the cyclic peptide identification, some protocols where the cycle is opened before MS analysis have been described. Here we propose a simpler alternative protocol for combinatorial cyclic libraries synthesis and ring opening before MS analysis. METHODS: The protocol designed consisted in: a) incorporation of Fmoc-Asp[2-phenylisopropyl (OPp)]-OH to Ala-Gly-oxymethylbenzamide-ChemMatrix (Ala-Gly-HMBA-CM) resin, b) synthesis of the combinatorial library on the resin by the divide-couple-recombine method, c) assembly of a glycolamidic ester by adding glycolic acid, d) couple of an Ala residue in the N-terminal position, e) removal of OPp with 4% TFA, f) peptide cyclisation on solid phase through side-chain Asp and N-Ala amino terminus, g) removal of side chain protecting groups with a 95% TFA cocktail, d) vapour phase aminolysis for simultaneous opening of the ring and release the peptide and e) matrix assisted laser ionisation mass spectrometry MSMS analysis. RESULTS: High quality mass spectra were obtained. Peptide signals were high and their sequences could be deduced from the tandem mass spectra of each single bead evaluated. CONCLUSIONS: The strategy herein proposed is suitable for the preparation of one-bead-one-cyclic depsipeptide libraries that can be easily open for its sequence by MS. It employs techniques and reagents frequently used for all peptide laboratories and therefore it is friendlier than other current strategies.